1. Field of the Invention
This invention relates to a method and apparatus for removing substances adhering to a surface, and more particurlarly to a method and apparatus for washing and stripping an outer surface of buildings or the like including substances adhering to the surface.
2. Prior Art
The external wall of a building gets dirty or contaminated by dust contained in air or rain with the passage of time. In general, the wall is needs to be renovated, for example by re-painting, every ten years or so. In case of a special kind of wall such as a so-called curtain wall, the wall should be washed every two or three years to remove dirt thereon. Or, as the case may be, there is a need for stripping a coating on the wall to expose a surface thereof.
Washing of the wall is generally carried out by using water or washing chemicals. When water is used, relatively high-pressure water of a pressure of about 40 to 200 kg/cm.sup.2 is jetted through a nozzle having a diameter of about 2mm at a flow rate of 25 to 45 l/min.
Stripping or eeling of the coating of the wall is carried out by using a sander, a chip-cleaner or a concrete-planer. Alternatively, chemicals are also used for stripping or peeling.
However, these conventional methods have various disadvantages. When chemicals are used in washing, there is no problem of dusting, but the chemicals usually contain acids and they give undesirable influence upon plants on the ground and possibly deteriorate or change the properties of the surface of the wall.
Sanding or planing can effectively remove dirt or contaminant on the wall together with a surface thereof, but it has such a fatal defect that it makes a dust, compromising the safety of the operator and contaminating the surroundings. If water is used in sanding or planing to prevent dusting the sander or planer will be clogged and the operation efficiency will be lowered.
In contrast, the method using high-pressure water is free from the problems as described above and it is advantageous in that water can be easily obtained at a low cost. However, the conventional method of this type is not satisfactory in that water is only jetted from a single nozzle and therefore washing or stripping is only made linearly when the nozzle is moved. Thus, the operation efficiency is extremely low.